Bug 1533425 - Look for architecture-specific greprefs.js files on Android r=njn
We want to publish a multi-architecture AAR for GeckoView which includes
a single omni.ja, but we archicture-specific changes in greprefs.js that
prevent this from working. This patch causes us to try to read an
architecture-specific greprefs.js first, which will be provided by the
packaging process for the fat AAR.
Differential Revision: https://phabricator.services.mozilla.com/D22526